12.1 Introduction
Crimes against humanity’s complicated origin story has generated confusion regarding its modern content and legal foundations. It has nonetheless become a critical component of modern international justice. This chapter explores the development of the crime in the twentieth century, including its evolution in customary international law and its codification in the Rome Statute of the International Criminal Court (‘Rome’ or ‘ICC Statute’). It also takes up the current proposal to re-codify it in a new, specialized, multilateral convention based upon the International Law Commission’s (ILC) 2019 Draft Articles on Crimes Against Humanity(‘Draft Articles’),Footnote 1 a project that 124 States have, thus far, explicitly committed to.Footnote 2 It identifies five phases in the crime’s development, from its nineteenth-century natural law origins through its codification in the ICC Statute, and finally its possible recodification in a new treaty.
Consistent with the theme of this volume, after exploring the historical genesis and current status of crimes against humanity in customary international law, this chapter evaluates the position of States as regards the unity, evolution, and diversity of their interpretative approach to the ILC Draft Articles and particularly the definition of crimes against humanity in Draft Article 2. Among State supporters of this new treaty, most have embraced the idea of unity in approaching the definition of crimes against humanity in the new treaty.Footnote 3 By unity, they seem to mean that the new treaty should essentially serve as a horizontal ‘add-on’ to the Rome Statute of the International Criminal Court (ICC), making the two instruments seamlessly consistent as a matter of text and application.
Other States, however, are tempted by the idea of evolution, which could adjust the definition to consider developments found in customary international law,Footnote 4 such as the prohibition on the slave trade or the emergence of new crimes.Footnote 5 Indeed, some States have suggested that the new treaty offers the possibility, consistent with Article 13 of the UN Charter, for progressive development and have proposed the addition of new crimes, including economic crimes,Footnote 6 environmental crimes,Footnote 7 and the crime of gender apartheid.Footnote 8 They agree with taking the Rome Statute definition as the centerpiece of the new treaty but have proposed or accepted modifications they believe will make it a treaty responding to the modern needs of the international community.
Finally, the Draft Articles themselves, like the ICC Statute, have also recognized that there may be a diversity of codifications in national legislation, and that customary international law may continue to evolve outside treaty codifications of crimes against humanity. This was the position of the ILC itself, which thus included a ‘without prejudice’ clause in Draft Article 2(3) to provide States with flexibility in adapting a new treaty to municipal law, so long as the definition they adopt is ‘broader’.Footnote 9
The consequences that might flow from national – or international – variations of the crimes are not spelled out by the Draft Articles, or by the Rome Statute, a point returned to periodically in Sections 12.2, 12.3, and 12.4. Yet, as evidenced by the 2021 judgment of the ICC Appeals Chamber in Abd-Al-Rahman, the relationship between treaty codifications of crimes against humanity, including the Rome Statute and customary international law, is important in considering the legality principle with respect to the prosecution of non-Rome Statute State Party nationals for ICC crimes or eventually in universal jurisdiction cases heard by national courts. The purpose of this contribution is not to evaluate these three approaches but to offer some reflections that may be useful to their consideration. This analysis is particularly important given the ongoing negotiations of a new treaty on crimes against humanity.
12.2 Historical Development of Crimes Against Humanity
In the mid-1990s, when the Rome Statute was being negotiated, the international community was experiencing a renaissance in the domain of international law and international lawmaking. Thus, when crises arose, including the collapse of the former Yugoslavia and its descent into war, and the 1994 Rwandan genocide, the response was, in part, to resurrect the project of creating international criminal tribunals and courts to address the commission of atrocities, which had lain fallow since 1945.
But it was not clear what law these new courts and tribunals apply, as the gap between the modern origins of international criminal law at Nürnberg and Tokyo and the efforts, some fifty years later, to enshrine these precedents in modern institutions was considerable. This was particularly true for crimes against humanity, which had no treaty basis prior to its inclusion as Article 6(c) of the Charter of the International Military Tribunal at Nürnberg (IMT Charter)Footnote 10 and Article 5(c) of the Charter of the International Military Tribunal for the Far East (IMFTE Charter).Footnote 11 Indeed, it was unclear whether the legal basis for crimes against humanity was a treaty, based on the status of the IMT Charter as a treaty signed by twenty-three States,Footnote 12 or a matter of customary international law, as later evidenced by its subsequent adoption by the General Assembly as the Nürnberg Principles of 1950.Footnote 13 It was unclear during the period of the crime’s emergence, and experts have debated this question for more than seventy years.Footnote 14
The IMT based its interpretation on the Charter it was given, famously noting that, in its view: ‘The Charter is not an arbitrary exercise of power on the part of the victorious nations, but […] the expression of international Law existing at the time of its creation; and to that extent is itself a contribution to International Law.’Footnote 15 Presumably, the IMT was referencing customary international law. That said, given a dearth of State practice or case law on crimes against humanity, the IMT construed Article 6(c) of its Charter (on crimes against humanity) relatively narrowly. For example, the tribunal required that crimes against humanity have a connection to the other crimes in the Charter (war crimes and/or crimes against peace) to be indictable, which eliminated persecutions committed by the Nazis in the 1930s, prior to the invasion of Poland, from the charges faced by the accused. It also found that the crime of persecution in Article 6(c) was not independent from the other crimes listed in the Charter (murder, extermination, etc.), a limitation later critiqued by scholars.Footnote 16
Nonetheless, three key ideas emerged from the text of the Charter and the Judgment of the Tribunal: (1) crimes against humanity, unlike war crimes, protect all civilians – including a State’s own nationals – from widespread or systematic attacks on certain human rights and persecutory campaigns; and (2) neither the accused’s official position nor national law is a defence. Finally, (3) the crimes themselves are particularly egregious, ‘characterized either by their seriousness and their savagery […] or by their magnitude, or by the fact that they were part of a system designed to spread terror, or that they were a link in a deliberately-pursued policy against certain groups’.Footnote 17
Because no treaty was ever adopted for crimes against humanity after the war,Footnote 18 other than its partial codification in the form of treaties on the crime of genocide (1948), and later apartheid (1974), torture (1984), and enforced disappearance (2006), crimes against humanity persisted in customary international law but without a firm treaty foundation. The ILC had undertaken but not finalized the task of codifying it along with other international crimes. The ILC had also drafted articles to be used in establishing an international criminal court, producing two separate documents in the 1990s, one for a Court in 1994Footnote 19 and one for a draft code of crimes in 1996.Footnote 20 Both texts referenced crimes against humanity, but neither was ready to serve as the basis of an international criminal court. Instead, when the Security Council established the ad hoc international criminal tribunals for the former Yugoslavia (ICTY)Footnote 21 and Rwanda (ICTR),Footnote 22 it did not rely on the Commission’s work but adopted Statutes annexed to Security Council Resolutions adopted under Chapter VII of the United Nations Charter for each of the two entities.
The Secretary-General’s Report supporting the establishment of the ICTYFootnote 23 stated that the Security Council would not be ‘creating or purporting to legislate’ but that the ICTY would have the ‘task of applying existing international law’.Footnote 24 The Report added:
In the view of the Secretary-General, the application of the principle nullum crimen sine lege requires that the international tribunal should apply rule of international humanitarian law which are beyond any doubt part of customary law so that the problem of adherence of some but not all States to specific conventions does not arise.Footnote 25
The Report suggested that the relevant treaties to be applied were the four Geneva Conventions of 12 August 1949, the Hague Convention (IV) Respecting the Laws and Customs of War on Land and the Regulations annexed thereto of 18 October 1907, and the Convention on the Prevention and Punishment of the Crime of Genocide of 9 December 1948, in addition to the Nürnberg Charter.Footnote 26
As for crimes against humanity, the Report noted the absence of a treaty thereon, a lacuna that the international community is endeavouring to fill at the present moment,Footnote 27 and to which this chapter returns in Section 12.3. Thus, the Report suggested, the Charter and Judgment of the Nürnberg Tribunal and Control Council Law No. 10Footnote 28 would be the relevant referents. In addition, the Report observed that ‘[c]rimes against humanity are aimed at any civilian population and are prohibited regardless of whether they are committed in an armed conflict, international or internal in character’.Footnote 29 Despite this, the armed conflict nexus was retained in the chapeau of Article 5 when the Statute was finally adopted.Footnote 30 Conversely, Article 3 of the ICTY’s sister tribunal, the IICTR excluded the ‘armed conflict’ element, but included a requirement that the crime be committed ‘on national, political, ethnic, racial or religious grounds’.Footnote 31 This tendency to codify the crime by adding new material elements depending on the facts of specific conflicts is a problem that persists today. I return to this point in Section 12.2.
Thus instructed, the two ad hoc tribunals began adjudicating cases and developing a modern jurisprudence of crimes against humanity as customary international law. Between them, 161 individuals were indicted at the ICTY,Footnote 32 and 93 at the ICTR.Footnote 33 In a 2013 study, I found that at the ICTY, crimes against humanity represented 40.6 per cent of all indicted offences, and war crimes charges approximately 56.9 per cent. Conviction rates were approximately the same for both the crimes against humanity charges and the war crimes charges (39.3 per cent and 37.5 per cent, respectively). Genocide charges were few, and convictions rare.Footnote 34
In 1999, the ICTY found that under customary international law, crimes against humanity could occur in peace time as well as during armed conflictFootnote 35 and rejected the idea that they must be accompanied by discriminatory intent.Footnote 36 The Kunarac decision also rejected the requirement that crimes against humanity could only be committed pursuant to a State or organizational policy.Footnote 37 Some of these important holdings, which, as noted above, were articulated as norms of customary international law, followed and therefore contradicted the earlier codification of crimes against humanity in Article 7 of the ICC Statute, which was adopted on July 17, 1998.
Subsequent decisions of both the ICTY and the ICTR also contributed extensively to an understanding of the murder-type crimes and the crime of persecution and elaborated a comprehensive jurisprudence on sexual and gender based violence as well.Footnote 38 As former ICTY Judge Patricia Wald has noted, ‘crimes against humanity [became] the growth stock of Tribunal jurisprudence’.Footnote 39 Meanwhile, as the ad hoc tribunals began their work, the ICC Statute was being negotiated, first in New York during the Preparatory Committee meetings held at the Headquarters of the United Nations and then in Rome during the summer of 1998.
12.3 The Codification and Development of Crimes Against Humanity at the ICC
12.3.1 The Negotiations at Rome
There was little doubt that crimes against humanity would be included in the Rome Statute, given its origins in the Charters of the Nürnberg and Tokyo Tribunals. That said, it had not been included as such in the 1991 Draft Code of Crimes against the Peace and Security of Mankind produced by the ILCFootnote 40 although it was reinserted in the 1996 text and was not within the automatic jurisdiction of the proposed court envisaged by the ILC in 1994.Footnote 41 During the Preparatory Committee meetings held prior to the Court’s Statute, it was agreed that the definition should reflect the elements of the crime under customary international law.Footnote 42
Yet ascertaining the content of that custom was challenging. Crimes against humanity had originated as natural law in the nineteenth century to condemn slavery and the slave tradeFootnote 43 and King Leopold’s atrocities in the Congo.Footnote 44 In the twentieth century, it began to take shape as customary international law, with the judgments of the Nürnberg and Tokyo Tribunals. The texts of the ICTY and the ICTR Statutes were another important source of customary international law, as were judgments from national courts, including the BarbieFootnote 45 and Eichmann cases, from the Supreme Courts of France and Israel, respectively. In Eichmann, in particular, the Israeli courts were exercising universal jurisdiction over the accused, as Israel was neither the State or the territory of which the crimes were committed, nor the State of the accused (or the victims) nationality. As the Supreme Court of Israel noted:
The abhorrent crimes … [are] crimes which offended the whole of mankind and shocked the conscience of nations are grave offences against the law of nations itself … in the absence of an International Court, the international law is in need of the judicial and legislative authorities of every country, to give effect to its penal injunctions and to bring criminals to trial. The jurisdiction to try crimes under international law is universal.Footnote 46
Thus, unlike war crimes and genocide, for which treaty texts were available, defining crimes against humanity during the Rome Statute’s negotiation required achieving a consensus as to which elements of the crime represented customary international law.Footnote 47 This was a considerable challenge in part because unlike the ad hoc tribunal statutes, which were drafted after the crimes had already been committed or as they were ongoing, and with a specific crime base in mind, the ICC was drafted for future cases.
The link to customary international law was also important because of the potential for worldwide application of the Rome Statute through the vehicle of a Security Council referral of a situation involving the nationals of non-State Parties. For this reason, as several contemporaneous accounts suggest,Footnote 48 the negotiators intended the Rome Statute to represent, like the ICTY and ICTR Statutes, customary international law and were not intending to create new law.Footnote 49 That said, they included some adaptations that would take into account the fact that a new court was being established to prosecute the crimes therein, which would have its own set of jurisdictional limitations and prosecutorial priorities. In the sense of the North Continental Sea judgment of the International Court of Justice,Footnote 50 there were elements of codification, crystallization, and customary international law creation at Rome as to crimes against humanity.Footnote 51 Much of the Statute tracked the Nürnberg definition (codification), some elements that had been debated in prior case law and by scholars were clarified, such as the severing of the link to armed conflict (crystallization), and others, such as the new provisions on sexual and gender-based violence, emerged as new crimes at Rome (creation).
Like other core international crimes, crimes against humanity are composite offences, comprising a material element (an actus reus), a mental element (mens rea), and a chapeau containing context elements that internationalize the crime and distinguish it from ordinary crimes like murder, torture, and crimes of sexual violence, for example. In crafting the chapeau containing the context elements of crimes against humanity, the drafters eliminated the element requiring a connection to armed conflict but retained in Article 7(1) the requirement of an ‘attack’ directed against a civilian population and that the attack on the civilian population be either widespread or systematic, rejecting the view that the attack must fulfill both requirements under customary international law. They also eliminated the requirement of discriminatory intent found in the ICTR Statute. However, they added, in Article 7(2)(a), a requirement that the crime be committed ‘pursuant to or in furtherance of a state or organizational policy’, an element that the ICTY and ICTR had rejected, and which many scholars believe is not required by customary international law.Footnote 52
The eleven offences in Article 7(1)(a) through (k) requires the actus reus of the offence be limited to violent attacks upon corporal integrity (and similar offences), tracking the Statutes of the ad hoc tribunals, but with important additions. The list of prohibited acts includes murder, extermination, deportation and forcible transfer, imprisonment, torture, rape, and other forms of sexual, gender-based, and reproductive violence, persecution, and a catch-all provision: other inhumane acts. The inclusion of ‘other inhumane acts’Footnote 53 raises the possibility of new atrocities emerging as crimes against humanity in the future. It has already been used to capture the crime of forced marriageFootnote 54 and has been charged in other ICC cases, including the Abd-Al-Rahman case, discussed further below. The drafters declined to add environmental and/or economic crimes as certain States had urged during the negotiations of the Rome StatuteFootnote 55 and as the ILC had discussed during its work on the Draft Code of Crimes. This possibility has reappeared in discussions pertaining to the new treaty discussed Section 12.4.
Unlike predecessor tribunals, the ICC operates in real time and with the link to armed conflict explicitly severed in the text of Article 7, it is now understood that crimes against humanity may occur in times of relative peace. Thus, crimes against humanity have emerged as a pivotal offence at the ICC and have been charged or alleged in virtually all the situations referred to the Court to date. In situations involving armed conflict, crimes against humanity charges often track war crimes charges or target persecution or sexual violence. In other situations, crimes against humanity are the only charges that can be brought in the absence of armed conflict (at least at the outset of the referral) and the implausibility of alleging genocide. Given the ubiquity of the crimes against humanity charges at the ICC, we see that the ICC has become, in many ways, a crimes against humanity court.Footnote 56
The early case law of the ICC defined the terms ‘widespread’ and ‘systematic’ with relative ease, relying upon jurisprudence from the ad hoc international criminal tribunals to do so. It also concluded that the ‘attack’ against the civilian population need not be a military operation. Prosecutor v Dominic Ongwen held that an attack under Article 7 must be ‘a course of conduct’, by which is meant a ‘series or overall flow of events, as opposed to a mere aggregate of random or isolated acts’ committed by a State or ‘organization’; the latter requiring only that ‘the organization has a set of structures or mechanisms, whatever those may be, that are sufficiently efficient to ensure the coordination necessary to carry out an attack directed against a civilian population’.Footnote 57
The meaning of ‘State or organizational policy’ has presented more difficulties of interpretation as it was not included as a context element at the ICTY or the ICTR. The Court addressed it first in connection with a request to open an investigation into the 2007 post-election violence that took place in Kenya, which the Prosecutor argued constituted a crime against humanity. In considering the Prosecutor’s request, a Majority of Pre-Trial Chamber II noted that the policy element was eventually abandoned by the ad hoc tribunals but drew upon earlier cases in examining the Rome Statute.Footnote 58 Finding that the plan to commit the attack may be inferred from the commission of ‘a series of events’, including a variety of factors,Footnote 59 using classic methods of treaty interpretation, the Majority read ‘state or organizational’ in Article 7(2)(a) disjunctively, rejecting the notion that only ‘State-like organizations may qualify’. Rather, examining its prior decisions, as well as the text of the Statute itself, the jurisprudence of the ad hoc Tribunals, and the travaux préparatoires including the work of the International Law Commission in elaborating the 1996 Draft Code of Crimes, it focused upon ‘whether a group has the capability to perform acts which infringe on basic human values’. The Chamber added that the organization need not be ‘State-like’, and that the policy need not have been conceived at the highest level of the State, for ‘regional or even local organs of the State could satisfy the requirement of a State policy’.Footnote 60 Although Judge Hans-Peter Kaul penned an influential dissent, contending that the organization must be ‘State-like’ for its policies to fall within the ambit of Article 7, the Majority view has prevailed at the Court.
At the Rome Conference, some delegations wanted to delete the words ‘civilian population’, arguing that they were imprecise and unnecessary, but this traditional limit on the ambit of crimes against humanity has remained. Thus far, the ICC has followed the ICTY, holding that the definition of ‘civilian’ in Article 50 of Additional Protocol I to the Geneva Conventions on the laws of war sets forth the relevant standard.Footnote 61 That said, as the ICTY has also held, the ICC has found that ‘despite the requirement that the attack be directed against a civilian population, there is no requirement that the individual victims of crimes against humanity be civilians for the purpose of international humanitarian law (IHL), but may include persons otherwise protected under this body of law’.Footnote 62 The Extraordinary Chambers in the Courts of Cambodia (ECCC) has recognized this in its judgments, as well.Footnote 63 This is logical: because crimes against humanity, unlike war crimes, can be committed in peacetime, the civilian/combatant distinction may not apply.
The crimes against humanity charged to date have included murder, extermination, torture, deportation or forcible transfer, rape, forced marriage, forced pregnancy, persecution, sexual slavery, and other inhumane acts, among others. The ICC, even with the small number of final judgments achieved to date, is thus generating significant and important jurisprudence setting out the elements for each of these crimes. Of particular significance, the Ntaganda and Ongwen decisions recognized sexual violence during wartime as a crime against humanity.Footnote 64 Ongwen added convictions for forced marriage as other inhumane acts under Article 7(1)(k) and forced pregnancy under Article 7(1)(g).Footnote 65
12.3.2 The Status of the ICC’s Definition as Customary International Law: The Abd-Al-Rahman Case
The Rome Statute exists in a complex international ecosystem. The drafters clearly intended to track customary international law because they intended the Statute to have universal application. While cognizant of the fact that at least in its early years, not all States would become party to the Statute, they nonetheless made ICC law (Rome law) potentially applicable to all persons worldwide through the Security Council referral triggering mechanism for the Court. In addition, under the doctrine of complementarity, the idea is that States would adopt national legislation allowing them to prosecute ICC crimes in order to assume their roles as the primary enforcers of international law. While the assumption may have been that States would ‘copy-paste’ the text of the Rome Statute into their national legislation, in fact many States have departed from the text of the Rome Statute considerably.Footnote 66 Even within the text of the Rome Statute itself, the drafters changed the elements of the crimes slightly and added new crimes, suggesting a certain evolution of international criminal law and creating diversity in the field by departing from the statutes of the ad hoc international criminal tribunals. Thus, the unity of international criminal law, its evolution, and its diversity were all present at the founding.
Given this evolution and diversity, the question remains whether it is fair and legal to apply Rome law to non-State Party nationals. This question arose and was less than satisfactorily addressed by the ICC Appeals Chamber in the Abd-Al-Rahman case. The defendant, Abd-Al-Rahman, was a Sudanese national accused of crimes against humanity and war crimes who had surrendered himself to the Court. He challenged the ICC’s jurisdiction, inter alia, on the basis that since Sudan was not a State Party to the Rome Statute at the time of the Security Council’s referral and the events underlying the charges against him, his prosecution violated the principles of nullum crimen sine lege and non-retroactivity ratione personae in Articles 22(1) and 24(1) of the Statute, unless those crimes were defined either in Sudan’s national law or in international treaties and customary international law applicable to Sudan.Footnote 67
The Pre-Trial Chamber made short work of the Defendant’s arguments, noting that the purpose of Articles 22 and 24 was to ensure that the Court ‘does not deviate from the intention of the drafters that it should apply the statutorily defined crimes, and no others’.Footnote 68 Looking to the importance of the Article 13(b) triggering mechanism included in the Statute permitting Security Council referrals, the Chamber reasoned that it would ‘call into question the very raison d’être of that particular triggering mechanism’ to suggest it could only be applied after a searching analysis of the legal obligations expressly accepted or included by the relevant StateFootnote 69 and declined to examine whether the crimes were prohibited under customary international law.Footnote 70
On appeal, the defence continued to challenge the legality of Mr Abd-Al-Rahman’s prosecution. The Prosecutor’s appeal brief noted that the ‘crimes set out in articles 6, 7, and 8 of the Statute are substantially similar to those in customary international law’,Footnote 71 and the Appeals Chamber concluded that the charges ‘draw upon norms that were recognized globally, including in Sudan, and were fully ascertainable at the time of the conflict in Darfur’.Footnote 72 Unlike the Pre-Trial Chamber, however, the Appeals Chamber examined the history of the referral under Security Council Resolution 1593 and noted that the Commission of Inquiry on violations of international humanitarian law and human rights law in Darfur had already reported on the conflict and included, in its reports, an analysis of the ‘framework of international human rights and humanitarian laws applicable in Sudan at the time; and found criminal violations thereof’.Footnote 73 Therefore, the Security Council’s referral ‘encompassed violations of binding international obligations carrying a risk of individual criminal liability’.Footnote 74
Unlike the ICTY and the ICTR, the ICC Appeals Chamber did not seem to agree that the Security Council referral alone solved the nullum crimen problem. Instead, it asserted that under the Rome Statute, it must be foreseeable that an accused could have reasonably expect to face prosecution, and the relevant laws must have been ascertainable, in the sense they were sufficiently clear and accessible to the accused.Footnote 75 The Appeals Chamber then added that the foreseeability test is not met simply because the ‘crimes charged can be found in the text of the Statute’. Rather, the Court based the legality of Mr Abd-Al-Rahman’s prosecution on the fact that the accused had spent a considerable part of his career as a non-commissioned officer in the military who had actual experience with the application of common Article 3 of the 1949 Geneva Conventions and was personally ‘in a position to understand and comply with his obligations in armed conflict under international law’.Footnote 76 Only after examining the personal familiarity of Mr Abd-Al-Rahman with the laws of war did the Appeals Chamber conclude:
[T]he Appeals Chamber notes, generally, that the statutory crimes [of the ICC] are a product of a concerted effort to codify the developing state of international law so as to provide the clarity that was lacking in the preceding international tribunals. In principle, the Appeals Chamber considers that the crimes under the Statute were intended to be generally representative of the state of customary international law when the Statute was drafted. This weighs heavily in favour of the foreseeability of facing prosecution crimes within the jurisdiction of this Court, even in relation to conduct occurring in a State not party to the Statute.Footnote 77
Thus, the Chamber found that the risk of international criminal liability was ‘acute to such a degree that it was foreseeable to an officer of Mr Abd-Al-Rahman’s rank’.Footnote 78
The decision of the Appeals Chamber suggesting that non-State Party Nationals are entitled to an individualized determination of whether the Rome Statute can be applied to them consistent with the legality principle raises serious conceptual and practical concerns. While certain authors have embraced the decision’s restrictive approach,Footnote 79 others have noted that it may lead to ‘disconcerting results, no sound normative principle supports it, and [it] […] does not correspond to the design of the creators of the ICC Statute’.Footnote 80
Indeed, it is hard to imagine how the Court will function if the norms in the Statute cannot be applied to individuals hailing from countries that have not joined the Court or whose national legislation does not include ICC crimes. At the present time, the list of non-State party nationals indicted or under investigation by the ICC for crimes committed either in their own jurisdiction (Sudan and Libya) or on the territories of other ICC States Parties or States accepting the jurisdiction of the Court is extensive. It includes the situation in Bangladesh/Myanmar, State of Palestine, and Ukraine, and before the preliminary examinations were dismissed also included the Registered vessels of the Comoros and the Situation in South Korea. It appears that some authors have embraced the notion of a ‘Court à la carte’ – which was the model rejected at Rome – due to a fundamental misapprehension of the principles underlying the ICC’s jurisdiction. A full discussion of this issue is not possible within the confines of this short chapter; however, as I have written elsewhere, jurisdiction is conferred by States upon the ICC, not ‘delegated’ to them, meaning that they do not transfer bits of their national sovereignty to the Court when they join but instead collectively confer power and authority on the ICC as an independent judicial entity.Footnote 81 The ICC is an international institution that, like the ad hoc tribunals for the former Yugoslavia and Rwanda, exercises the ius puniendi of the international community.Footnote 82
Crimes against humanity have been identified as crimes that the international community and States have a shared responsibility to protect under paragraphs 138 and 139 of the 2005 World Summit Outcome Document,Footnote 83 as jus cogens offences by the International Law Commission,Footnote 84 and have been included in every international criminal court and tribunal Statute established since the Nürnberg tribunal except for the Special Tribunal for Lebanon. Moreover, Article 7 is increasingly seen by international and national courts and tribunals, including the ICTY, the European Court of Human Rights, the Inter-American Court of Human Rights, US federal courts, and the UK House of Lords, as codifying the customary international law of crimes against humanity.Footnote 85 Since there is no treaty on crimes against humanity, many States also have no legislation on crimes against humanity.
The Appeals Chamber’s decision in Abd-Al-Rahman raises the specter that certain Rome Statute crimes might be opposable vis-a-vis certain accused whereas others would not, depending on the national legislation in force at the time and place the crimes occur. This would mean that the ICC’s judges are incorporating through the backdoor by means of judicial interpretation arguments raised about the Rome Statute that were rejected during the negotiations. Indeed, the ICC judges were conceptualizing the ICC as if it were a foreign court operating under the principle of universal jurisdiction, where double criminality might indeed pose difficulties. In 2021, a panel of the French Cour de Cassation found that a Syrian national could not be tried for crimes against humanity under universal jurisdiction because Syria had not criminalized crimes against humanity, which violated the principle of double criminality.Footnote 86 This was reversed by the full Court, which found that the underlying acts of murder, rape, and torture were criminal, and therefore the prosecution could proceed. That holding notwithstanding, the Court noted that certain war crimes and the crime of persecution could not be prosecuted in France under universal jurisdiction.Footnote 87 It did not consider the possibility that those crimes could be tried under customary international law.
12.4 The Proposed New Crimes Against Humanity Convention and Its Relationship to Customary International Law
12.4.1 Article 7 of the Rome Statute: Theme and Variations
I have asserted in this chapter that Article 7 of the Rome Statute codified, crystallized, and to a limited extent created a customary international law of crimes against humanity in 1998, and that this body of law can fairly and legally be applied to the nationals of State and non-States parties by the Court. In one important aspect, it is narrower and more restrictive than customary international law in requiring proof of a State or organizational policy. In other limited ways, it is modestly more progressive as a limited number of new crimes were added to the text. It is also evident that the Rome Statute codification is different than the texts of the various ad hoc tribunals. Finally, there are variants of crimes against humanity in national legislation. What is to be done about the various iterations of this crime in national and international law?
During the Rome Statute’s negotiation, recognizing this, the late Professor M Cherif Bassiouni, who chaired the Drafting Committee at Rome, proposed the inclusion of a provision in the future court’s statute to endeavour to preserve the existence of customary international law outside the Rome Statute.Footnote 88 It was incorporated as Article 10, which provides that ‘[n]othing in this Part of the Statute shall be interpreted as limiting or prejudicing in any way existing or developing rules of international law for purposes other than this Statute’.Footnote 89 Thus, the ICC Statute itself envisages that, like war crimes, crimes against humanity in the Rome Statute emerged from customary international law, represents a partial codification of customary international law, and remains in relationship to customary international law, which may continue to develop outside the Rome Statute itself in both national and international courts. The implication of this for the new treaty on crimes against humanity is discussed below.
12.4.2 Drafting a New Crimes Against Humanity Convention: Unity, Diversity, and Evolution
Returning to our theme of ‘unity, diversity, and evolution’, the negotiation of a new multilateral treaty on crimes against humanity has evinced the same trends and instincts manifested during the negotiation of the Rome Statute and its subsequent interpretation by the Court and in academic writings. As noted earlier, States are in the process of discussing a new treaty on crimes against humanity.Footnote 90 This conversation has been ongoing ever since the Crimes Against Humanity InitiativeFootnote 91 published a Proposed Convention on the Prevention and Punishment of Crimes Against Humanity in 2010.Footnote 92 Attention increased after the ILC added ‘crimes against humanity’Footnote 93 to its long-term programme of work in 2013. In October 2019, the second (final) set of draft articles was taken up by the United Nations General Assembly’s Sixth Committee, which considers legal issues.Footnote 94 After six years of consistent advocacy by States and civil society, the treaty has finally been sent to negotiations by the UN General Assembly on the basis of consensus, after significant negotiations occurring during the Fall of 2024.Footnote 95 Pursuant to Resolution 79/122, the negotiations will begin in 2026 with the convening of a Preparatory Committee that will meet in two sessions (2026 and 2027), followed by two rounds of treaty negotiations at a UN Diplomatic Conference to take place in 2028 and 2029.Footnote 96 During the negotiations in 2024, 124 States voiced support for moving forward,Footnote 97 and a declaration supporting the adoption of a new treaty was adopted and circulated by more than 650 civil society organizations and individuals from around the world.Footnote 98 Resolution 79/122 was adopted without a vote by the General Assembly and on the basis of consensus by the Sixth Committee; however, the Russian Federation dissociated on both occasions. Given that negotiations on the new treaty will begin in earnest in 2026, the question of how the crime should and will be defined remains on the table.
12.4.2.1 Unity and Evolution
When it adopted a model draft treaty in 2010, the Crimes Against Humanity Initiative took the view that the definition of the crime in a new treaty should track the Rome Statute. Most participants in the meetings held in St Louis and The Hague in 2009 were of the view that the ‘convention must complement the Rome Statute and do no harm to the ICC’.Footnote 99 The International Law Commission took the same position, based upon the large number of States already adhering to the Rome Statute. The Commission also wished to support and promote the harmonization of existing international law.Footnote 100 Thus, Draft Article 2(1) and (2) of its text was drawn almost verbatim from Article 7(1) and (2) of the Rome Statute of the Rome Statute, with three exceptions, two of which, the deletion of the definition of genderFootnote 101 and the narrowing of the definition of persecution, were substantive.
At the same time, paragraph 2(3) contains a ‘without prejudice’ clause, making it clear that inclusion of the Rome Statute’s definition was without prejudice to broader definitions that may exist in international instruments, customary international law, or national law. Indeed, the ILC, notably, did not see its task as reflecting customary international law in the new treaty’s definition. Rather, in the Commission’s view:
While some aspects of these draft articles may reflect customary international law, codification of existing law is not the objective […] rather, the objective is the drafting of provisions that would be both effective and likely acceptable to States, based on provisions often used in widely adhered to treaties addressing crimes, as a basis for a possible future convention. Further, the draft articles are without prejudice to existing customary international law.Footnote 102
Particularly over the last two years, meeting pursuant to a structured meeting schedule and clear rules for debate set forth in Resolution 77/249 and organized by the Bureau of the Sixth Committee, States have debated whether or not a new treaty on crimes against humanity should take Article 7 of the Rome Statute as a given. Delegations have urged caution in amending the existing definition given that it was difficult to achieve consensus on the definition of crimes against humanity at Rome. Thus, the case for ‘unity’ is a strong one, particularly given the delicate compromise achieved in 1998.
At the same time, a trend away from ‘strict’ unity towards evolution has become evident during the past two years. This seemed particularly true during the April Resumed Session of 2024, held from 1–5 April 2024, during which many States expressed the view that evolution has taken place over the past twenty-five years and minor changes, reflecting the current state of the law, could and should be accommodated.Footnote 103 In their view, while the overall goal was a clear, stable, and useful definition of crimes against humanity, the treaty should function as a ‘floor’, not a ‘ceiling’, as some States might wish to adapt the definition in their national law by eliminating the policy element, for example, if they believed it was more consistent with customary international law. Many States suggested that this should be particularly so given that elements were added during the Rome Statute’s negotiation as jurisdictional filters to avoid overloading the docket of the Court and to reinforce the principle of complementarity. Thus, the preoccupation would not necessarily apply to a crimes against humanity convention implemented directly by States at the horizontal level.Footnote 104
12.4.2.2 Diversity
During the final Resumed Session of the Sixth Committee, which met between 1–11 April 2024, two trends seemed apparent. First, even the large group of States Parties to the Rome Statute, which have been generally supportive of the crimes against humanity treaty, expressed openness to consider a limited number of changes to the text, as discussed above.Footnote 105 Another quite small group, led by China, that is not supportive of the treaty, has suggested that the ILC needs to go back and study State practice.Footnote 106
In terms of the issues and amendments currently on the table, several are worth noting. These are helpfully summarized by Written Chair Summary of the last two years Resumed Sessions, as well as the Oral Report of the co-Facilitators of the Sixth Committee session.Footnote 107 Issues have been raised regarding sexual and gender-based crimes, as well as reproductive violence. Many, but not all, States have expressed support for the Commission’s decision to remove the definition of gender in Article 7(3) of the Rome Statute, finding it to be outdated. Other suggestions have been the inclusion of forced marriage as a new crime. A proposal has also been advanced to amend the crime of forced pregnancy and recognize the existence of other forms of reproductive violence.Footnote 108 An amendment to Draft Article (2)(1)(g) has been proposed to add ‘sexual or reproductive violence’ (proposed additional text is italicized) to recognize grave violations of reproductive autonomy that may exist in addition to the two codified crimes. Finally, a proposal is on the table to amend the definition of apartheid in Draft Article 2(1)(j) by adding gender apartheid to the text.Footnote 109 While the inclusion of forced marriage would be a codification of a customary international law development, given its adjudication by three international criminal courts to date as an ‘other inhumane act’, the addition of new crimes involving reproductive and sexual violence, and the inclusion of gender apartheid, would involve either the crystallization of an emerging norm or the inclusion of a new norm of international criminal law as these crimes have not yet been accepted as part of existing state practice.
Another set of changes proposes amending the definition of enforced disappearance in Draft Article 2(2)(i) to bring it into line with the 2006 International Convention for the Protection of All Persons from Enforced DisappearanceFootnote 110 and another would broaden the definition of persecution in Draft Article 2(1)(h) either by removing the necessity of a linkage between this crime and one of the other crimes entirely or expanding the crimes for which the linkage could be established.Footnote 111 A proposal that has received widespread support and is being championed by Sierra Leone is to add the slave trade to Draft Article 2(1)(c). Sierra Leone has also tabled a proposal to submit amendments on slavery and the slave trade to Articles 7 (crimes against humanity) and 8 (war crimes) of the Rome Statute. Finally, as mentioned earlier, other possible new offences have been of interest to States including colonialism, starvation of a civilian population, environmental crimes and ecocide,Footnote 112 unilateral coercive measures against civilians, terror related acts, use of nuclear weapons, exploitation of natural resources, and crimes against indigenous peoples.Footnote 113 While many of these suggestions have not yet been advanced as formal proposals, over the next three years, as the treaty gets negotiated, there will be an opportunity for them to do so.
12.5 Concluding Thoughts
As discussed earlier, crimes against humanity exist in a complex international ecosystem. They emerged first as a natural law objection to slavery and the slave trade that was found legally wanting even if morally compelling. Only later, in the first half of the twentieth century, faced with the horror of the Holocaust, did they find footing in treaty and customary international law. They were then codified and crystallized as treaty law in the guise of the Rome Statute and are now used by national systems in achieving post-conflict justice and in universal jurisdiction casesFootnote 114 and at the ICC. Through judicial development at the ad hoc tribunals, national courts, and later at the ICC, the overall contours of this crime now appear to be relatively well-settled although different iterations continue to appear in international law statutes, national legislation, and customary international law. This diversity of text and its application by national and international courts and tribunals has allowed the crime to evolve more freely than, for example, war crimes, which are heavily codified in international treaties, so as to respond to new manifestations of criminality or even highlight long-standing injustices such as colonialism and the slave trade that have historically been condemned but left outside modern texts of international criminal law. The potential expansiveness of this offence, however, has raised questions of legality and fairness to the accused, which have been explored in national and international courts.
What does this mean for the re-codification of this crime in a new treaty? While the ILC largely transplanted the Rome Statute definition of the crime into its draft text, as did our non-governmental project, there now appears to be a certain appetite for change amongst States and members of civil society. This is understandable, for, as Carsten Stahn recently wrote, the Rome Statute is ‘still modern, but with growing age, it also gains wrinkles’.Footnote 115 Each of these codifications is seen as a ‘floor’ rather than a ceiling; a minimum ‘must have’ that States must incorporate in order to comply with their treaty obligations. If the Rome Statute is the current floor, any additions in the new crimes against humanity treaty would presumably not be more restrictive but would potentially add new crimes to the eleven now found in Article 7 of the Rome Statute. At the end of the day, however, States will have to decide how to manage their treaty obligations, and some may not wish to ratify a new treaty that has a different definition than the Rome Statute, particularly if they are required to amend existing national legislation to do so.Footnote 116
Of course, a large number of Rome Statute State Parties never incorporated crimes against humanity in their national laws, because the Rome Statute does not actually require them to do so. Instead, the preamble speaks only of a general ‘duty’ of States to prosecute international crimes.Footnote 117 And the sixty-eight or so non-ICC Party States will presumably not find themselves in a conflictual position. The United States, for example, does not currently have national legislation on crimes against humanity, and Ukraine did not until very recently. Thus, it may be both desirable and achievable for States to amend the definition of the crime in negotiating the new treaty. Finally, States are not required to copy-paste either the Rome Statute or the definition of the new treaty into their national law; while they arguably would not be in compliance with the new treaty if they adopted more restrictive provisions than those provided for in the text, Draft Article 2(3) as it currently stands allows them to adopt more expansive definitions, so long as the definition is ‘broader’.
In its Draft Articles, the ILC took a positivist approach, suggesting at one point in the commentaries that any deviation from the definition would mean that a State could not rely upon the rest of the treaty in terms of cooperation, etc.Footnote 118 Yet although modifications of the definition might under some circumstances raise questions under the doctrine of double criminality with respect to mutual legal assistance, assuming the variations are ‘material’,Footnote 119 they are not usually firm impediments to interstate cooperation. This comment by the Commission represents a shift away from the universalist approach of the Rome conference itself,Footnote 120 towards a more restrictive approach to even the most serious international crimes.
The preamble of the Draft Articles notes the jus cogens status of crimes against humanity. The question of what this means is vitally important for the functioning of this possible new treaty. In the Furundžija case, decided during the same period as the Rome Statute’s negotiation and adoption, the ICTY found that the peremptory status of the norm against torture meant not only that States had a duty not to commit torture but that they were permitted to try or extradite individuals accused of torture on the basis of universal jurisdiction, could not be subject to any statute of limitations, and were crimes of a ‘universal character’.Footnote 121 Both the proposed draft treaty and the Rome Statute itself envisage the possibility that States might develop new iterations of crimes against humanity, that may, in turn, create new customary international law. Thus, even with the re-codification of crimes against humanity in a new treaty, the need to consult customary international law both in the interpretation of that instrument and in terms of its continued development, will remain important. In this way, the crime will continue to evolve as a matter of customary international law, and we can expect to see a certain degree of divergence from the Rome Statute and diversity even in national laws on the subject. While mindful of the need for clarity and uniformity to protect to the rights of the accused and ensure that States understand their obligations of prevention and punishment, a certain degree of flexibility – such as we have seen in adjudications of crimes against humanity over the past thirty years – will allow this important category of international crime to remain a critically important legal protection for civilians, in peacetime and during armed conflict, from egregious attacks on their dignity and security.
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